The purpose of this application is to conduct an evaluation of a synchrotronradiation based x-ray optical system for transvenous coronary angiography. The intense and tunable synchrotron radiation produced at electron storage rings provides a source of X-rays uniquely suited to iodine k-edge DSA. The high intensity and small angular divergence permit the radiation to be monochromatized by Bragg diffraction and made available in beams of small vertical size, of arbitrary horizontal width, and of tunable energy. The use of such beams provides maximum sensitivity to intravascular iodinated contrasts agents and virtually eliminates image contrast due to non-vascular body structures. The brightness of the beams permits short exposure times and allows images to be recorded, in line-scan fashion, in sharp focus despite arterial motions. Work by the investigators at the Stanford Synchrotron Radiation Laboratory (SSRL) has demonstrated the principles of k-edge DSA using phantoms, excised animal hearts and anesthetized dogs. An X-ray beam at SSRL has been widened to 123 mm, a matching optical system has been assembled, a patient examination room has been constructed and fully equipped, and an initial evaluation in human subjects has taken place. The facilities at SSRL and a similar installation at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory will be used to optimize the parameters for synchrotron radiation transvenous angiography with the aim of improving the quality of the transvenous images so that they are comparable to those provided by the contentional arterially invasive technique. Efforts will then be made to reduce the invasiveness of the transvenous method by using peripheral injections of contrast agents, administered in reduced volumes and at reduced rates. In addition, preliminary studies of carotid and cerebral angiography will be done in human subjects.